Brief Answer:
Read below.

Detailed Answer:
I read your question carefully and I understand your concern.

Some degree of tremor of the fingers is normally present in many people when maintaining a certain posture. It can be exacerbated by taking stimulants like coffee or energy drinks, stress qnd anxiety as well. Other possible cause could be thyroid dysfunction or electrolyte abnormalities. Long term alcohol abuse or medication side effects could be the culprit as well.
After mentioning those causes I would also add that in a percentage of cases no causes can be found especially in the elderly. Most times it's of a psychological origin, related to anxiety issues.
What I suppose matters the most is that that type of trembling involving only the small fingers on both side is not a manifestation of any neurological condition like stroke, Parkinson's or other neurodegenerative diseases.

I remain at your disposal for further questions.

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